The invention relates to a method and an automatically functioning apparatus required for the execution of the method for the rolling of predominantly profiled rings, for example anti-friction bearing rings, with diameter enlargement in two rolling steps in one working sequence for the considerable reduction of the stress on the rolling mandrel. The invention can be used preferably in the anti-friction bearing industry for the production of anti-friction bearing rings of relatively small diameters for which, up to now, there has been required a finishing machining.
For the production of ring-shaped workpieces there are known several rolling methods and apparatuses, which predominantly function according to the roller-mandrel principle.
The workpiece is mounted on the mandrel and is re-shaped between the mandrel and the roller such that under the effect of the re-shaping force, the thickness of the wall is reduced, and at a width which is kept constant, the diameters are enlarged. During the re-shaping there occurs, in particular, a strengthening of the material of the ring and as a result thereof, an increase of the required rolling force.
For the rolling of profiled rings, for example, anti-friction bearing rings, there is required a minimum wall thickness of the initial part so that the profile can be completely rolled out. Because of the constant width and the constancy of volume, thus there result relatively small diameters for the initial part, whereby the borehole diameter determines the maximum possible mandrel diameter.
The mandrel of very small rolling diameter, which is due to the flow of the raw material, has to transmit in the end phase the maximum required re-shaping force, which leads to high stresses in the rolling mandrel. As an essential disadvantage, the practicability of the method is therefore limited to small ring diameters.
The object of the invention is to eliminate the aforementioned disadvantages of the prior art and to make rolling technically and economically applicable even for rings of relatively small diameters by eliminating the up to now required finishing machining, realizing with stabilization of the entire rolling process and reduction of ancillary time a considerable material saving at high working productivity.